This invention relates to a method of braking railguided vehicles, particularly locomotive-drawn railroad trains, automatically and accurately with respect to a deceleration distance, while using a computer which, in accordance with a predetermined function based on either time or distance, delivers speed values to means controlling the braking force of the vehicle. More particularly, the present invention is directed to an improved method of this type.
For automatic target braking, it is known to use digital or analog computers which compute the respective needed reference speed as a function of the distance to be covered, i.e., the distance from the instantaneous position of the vehicle to the target point where the vehicle is to be stopped or its speed reduced to a preset value. This is expressed, for a definite constant deceleration, by a speed-distance function which, in graphic representation, follows a parabola (desired speed or stopping distance parabola) and corresponds to the desired speed variation for a braking ending with a stop or at a preset reduced speed. Upon the braking command, the speed controller tries continually, by increasing the braking force or releasing the brake, to adjust the actual speed of the vehicle to the desired or reference speed predetermined by the braking-distance parabola.
Conventional braking systems, particularly air brakes, have considerable build-up, release and dead times. For example, the building-up of the brake pressure in locomotive-drawn freight trains takes 30 to 45 seconds before the desired braking force becomes fully effective. The release of the brakes takes a still longer period of time, about 1.5 times more. These considerable delay times do not permit a sudden application or release of the brake. Due to the variety of the masses to be braked (different train lengths and loads) as well as to the topography of the track with grades in both directions, constant decelerations are hardly obtainable, so that the variables depending thereon, such as the distance covered during the braking, are influenced by casual factors and fluctuate largely.